class 名字每个首字母大写，无空格
package 名字小写   com.jc

框架
package com.jc;

public class Hellofirst {
	public static void main(String[]args) {
		
	}

}

Hello Java代码
package com.jc;

public class Hellofirst {
	public static void main(String[] args) {
		System.out.println("Hello Java");
	}
}

print和println的区别
package com.jc;

public class HelloSecond {
	public static void main(String[] args) {
		System.out.print("你好");
		System.out.println("同学们.输出后会换行");
	}

}

无作用
System.out.print();
换行
System.out.println();

要输出反斜线
package com.jc;

public class HelloEscape {
	public static void main(String[] args) {
		System.out.println("\"Hello Java");
		System.out.println("要输出反斜线\\");
	}
}

package com.jc;

public class HelloMulti {
	public static void main(String[] args) {
		System.out.println("你好");
		System.out.println('好');
		System.out.println('A');
		System.out.println("");
		System.out.println("空字   符串");    //双引号内可以空字，符串
	    
		System.out.println('9');  //单引号也可以
		
		System.out.println(9);   //没有引号也可以
		System.out.println(18); 
		System.out.println(1.85);
		System.out.println(true);   
		System.out.println(false);
		System.out.println(0XF);
		System.out.print(017);
		System.out.println(0b1111);

        System.out.println("\u5403\u996d\u4e86");
	}
}


